Team Flare Lysandre

Walkthrough: By taking the right set of stairs, you will have to make it through rooms with Meowth Statues. If you land in the sight of one of these statues, you will get sent back to the beginning of the room. However, you can change their sight direction by clicking on the back of the statues. At the end of these rooms will be another room, the same that has the Leader of Team Flare, Lysandre, within.

As you come to Lysandre, he will mention how he had just unleashed the Ultimate Weapon in his universe to end all foolish life, only being transported to this universe as he did. He will then give your player the choice between two buttons: one will open the warp path in Lusamine's Room while the other will unleash the Ultimate Weapon. No matter which you choose, it will activate the Ultimate Weapon. You can stop the Ultimate Weapon by pressing the other button, but before allowing you to do so, you must first battle Lysandre.

Team Flare Lysandre - Level 65 Mienshao, Level 65 Pyroar, Level 65 Honchkrow, Level 65 Mega Gyarados, Level 67 Xerneas

After defeating him, you will be able to click the other button. Lysandre will then mention that if his world had someone like you, then perhaps he wouldn't have succeeded in his goal. The warp portal in Lusamine's Room will then open.